NASA is ready to get its best-ever look at Mars, courtesy of a spacecraft that's been on its way to the Red Planet for seven months.
Later today, the Mars Reconnaissance Orbiter is supposed to fire its engines and slow itself down enough to be captured into the planet's orbit.
The people at NASA's Jet Propulsion Laboratory in Pasadena, California, will be on pins and needles.
During the 27 minute engine-firing, the spacecraft will disappear behind Mars, and there won't be any radio contact.
It won't be until nearly an hour later that engineers will find out if the maneuver is successful.
If everything goes as planned, the craft will go into an orbit as low as 250 miles above the planet's surface.
Over the next seven months, it'll dip into the upper atmosphere and tighten the orbit.
In November, it's supposed to start collecting information on Mars.